Vulcanization of rubber and product obtained thereby



United States Patent O V I T1118 invention relates tov a new class of thiazolesulfenamides Which.new class of compounds is characterized by strong catalytic activity for accelerating the vulcanization of sulfur-vulcanizable rubbers.

In accordance with this invention it that thiazolesulfenamides of the structural formula where n is a whole number, where R and R are hydrogen or hydrocarbon radicals and where R" is a primary amine residue or a 6- membered heterocyclic secondary amine residue containing a hetero nitrogen atom at tached to the sulfur atom, are a class of highly useful vulcanization accelerators for sulfur-vulcanizable rubbers.

The monothiazolyl compounds falling within thescop'e of this invention are those of the aforedescribed., formula wherein n is one. Typical examples of this group. are. those wherein R1is a primary amine residuejof the. structure 'N l :1 where A is methyl, ethyl, n-propyl, isopropyl, n-but yl, sec-butyl, isobutyl, tert-butyl, n-amyl, isoamyl, secf' amyl, n-hexyl, 2-ethylhexyl, cyclohexyl, a-methylcyclo hexyl, a-ethylcyclohexyl, furfuryl, tetrahydrofurfuryl, benzyl, fl-phenethyl, 2-hydroxyethyl, S-hydroxy-n-propyl, hydroxy-tert-butyl, and the like.. Of'this group the thiazolesulfenamides wherein A is a branched chain alkyl radical, especially one having a tertiary carbon linked to the nitrogen; e. g. tert-butyl, are preferred; 1

A particularly valuable group of compounds wi the new class of thiazolesulfenamides are those in :which R" is a 6-membered heterocyclic secondary amine 'resie due such as morpholinyl, piperidyl, m-methyl piperidyl,-; 'y-methyl piperidyl, and like heterocyclic secondary amine residues. bis-thiazolyl sulfenamides of'piperazine and the yarious alkyl substituted piperazines such as LS-dl ll'lethYIrPl-j Other bis-thiazolyl sulfenamides falling within the scope of the present invention are those of the afore described formula wherein n is two and wherein R "'is Mo., a corpora- 5 has been found 15 Also included in this valuable group are thej;

In fgeneralit, is preferred that R and R in the fore-. going formulae be a short chain alkyl radical such as methyLethyl, propyl, and butyl, but it is to be understood that: higher alkyl radicals suchv as amyl, hexyl, octyl,

etc.; as we1l as alicyclic radicals suchas cyclbhexyl, aralkyl radicals such as benzyl, phenethyl, and. aryl radicals such as phenyl, tolyl, xylyl, and the like are" It is particularly preferred that R and also suitable. R'be methyl or ethyl radicals.

The new thiazolesulfenamides of this invention may be prepared from the corresponding mercaptothiazole and appropriate amine bycondensing these reactants in the presence of an oxidizing agent, as for example chlorine, hypochlorite, hydrogen peroxide and ammoniumfpersulfate. i

As illustrative 'of the new thiazolesulfenamides and the preparation thereof is the following:

EXAMPLE 1' 4-rr lethy l- 2 fi4-morpholinylsulfenyl) 5-thiazolecarboxylic acid Q aqueous solution containing 43.8 grains (0.25]v

mole) of '2-mercapto14-methyl-5-thiazolecarboxylic acid (Beil., 4th edition, vol. 27, p. 339), grams of water,

and 40.0 grams (0.25 mole) of a 25% aqueous sodium hydroxidesolution was prepared in a one liter 'narrow' beaker equipped with a mechanical mixer, dropping funnel, ice bath, and thermometer. 15 C., 65.5 grams (0.75 mole), of morpholine ,was added at such a rate that the reaction did not exceed a'temperature of 27 C. The

wise at 13'15 C. in 20 minutes.

extract washed with water until the washings were neutral to litmus, dried over sodium sulfate, and finally the ether removed in vacuo. The residue was a whitesolid. M; P. 56-57 C. Analysis gave 10.34% nitrogen and 24.75% sulfur as compared to 10.76% nitrogen and 24.63% sulfur calculated for C9H12N2O3S2.

EXAMPLE 2 I 4-(5-carbethoxy-4-methyl-2 thiazolylsulfenyl) morpholir te An aqueous solution containing mole) of sodium hydroxide in 200 ml. of .water, and 104.5

grams (1.2 moles) of morpholine was preparedin a two liter beaker equipped with a mechanical mixer, dropping funnel, and a thermometer. To this solution at 25 C., there was added, drop by drop, with-stirring over a period of two and one-half hours, 30.6 grams of iodine dissolved in 400 ml. of water containing 40 grams of potassium iodide. After about one-tenth of the'iodine solution had been added, the sulfenamide began to .sep arate:-in the form of white crystals. filtered off, washed with water until and air dried 'at room temperature. white solid, M. P. 53-54 C., was obtained in 66% yield. Theyield was somewhat better by the following procedure:

Heptane (1200 ml.) and 39 charged in a two liter, three-necked flask, equipped with To this, solution, at

mixture was cooled to. 13C. and 42 ml. of 25 sulfuric acid was added drop- To this mixture at 13 j-20 C. there was added, drop by drop, with stirring The excess sodiumhypo- The reaction mixture was cooled to 10f -C.,- extracted with500 ml. of ethyl ether, the ether 1 24.4 grams (0.12 1 mole) of S-carbethoxy-4-methyl-2-thiazolethiol (Levi, Ga'zz. 'Chem.,Ital. 61, p. 723-4931), 9.6 grams (0.24

The product was free from alkali, J The 'product, 'a

grams (0.0964 mole) of 2,2, dithio bis (5-carbethoxy-4-methyl thiazole) were grams (0.22 mole) of morpholine was added to this solution. Thereaction mixture was heated at 50 C. for one hour. After cooling to 25 (3., the morpholine salt of the mercaptothiazole was recovered by filtration. The filtrate wasextracted with 500 ml. of 2% aqueous sodium hydroxide, then washed with water until the washings were neutral to litmus, and the heptane was removed in vacuo at 35-40 C. The residue was cooled to 10 C.,

and the precipitate filtered off, washed with water, and air dried at 25 C. The product, a white solid, M. P. 53-54 C.', was obtained in 76% yield. Analysis gave 9.70% nitrogen and 22.49% sulfur as compared to 9.71% nitrogen and 22.23% sulfur calculated for CnHrNzOsSz.

. EXAMPLE 3 added the sulfenamide began to separate in the form of white crystals. The product was filtered off, washed with water until free from alkali and air dried at room temperature. A white solid, M. P. 123-l24 C., was obtained in 38% yield.

Qxidation with sodium hypochlorite as follows gave better results: An aqueous slurry was prepared containing" 50 grams (0.26 mole) of -carbomethoxy-4-methyl Z-thiazolthiol, 150 gramsof water, and 24.8 grams (0.29 mole) of morpholine in a one liter narrow beaker equipped with a thermometer, mechanical mixer, dropping funnel, and hot water bath. To this mixture, at 5 05 2 (1., there was added, drop by drop with stirring in 50 minutes, 160 mi. (14.6 g./ 100 ml.) of sodium hypochlorite. After cooling to C the precipitate was filtered off, washed with water until the washings were neutral to litmus, and air dried at room temperature. The product, a white solid, was obtained in 78,5% yield. After recrystallization from, ethyl alcohol, it melted at 123124 C. Analysis gave 10.00% nitrogen and 23.50% sulfur as compared to 10.21% nitrogen and 23.38% sulfur calculated for CmHmNzOsSz.

Employing the second procedure of Example 3 but replacing morpholine with an equimolecular proportion of piperidine there is obtained S-carbomethoxy-N-piperidyl-4-methyl-2-thiazolesulfenamide.

Employing the second procedure of Example 3 but replacing morpholine with an equimolecular proportion of piperazine there is obtained 1,4-bis-(S-carbomethoxytmethyl-2-thiazolylsulfenyl)piperazine.

. EXAMPLE 4- 4-(5 carbobut0xy-4-methyl-2-tkiaz0lylsulfenyl) morpholine An aqueous solution containing 115.5 grams (0.5 mole) of- S-carbobutoxy-4-methyl-2-thiazolethiol, 160 grams of 25% aqueous sodium hydroxide and 436 grams (50 sumed in the addition of this solution and stirring was con tinued for another half hour and the reaction mixture cooled to 10 C., the solids filtered off and washed until thewashingswere neutral to litmus. The semi-solid prod- 5 -carb0methoxy-N -cyclohexyl-4 -methyl-2-thiaz0lesalfenamide The yield was 66 An aqueous solution containing 45 .4 grams (0.24 mole) of 5-carbomethoxy-4-rnethyl-2-thiazolethiol, 77 grams of 25% aqueous sodium hydroxide in 200 ml. of water, and 237.6 grams (2.4 moles) of cyclohexylamine was prepared in a two liter beaker equipped with a mechanical mixer, dropping funnel, and a thermometer. To this solution at 25 0., there was added, drop by drop, with stirring over a period of two hours, 91.7 grams of iodine dissolved in 1200 ml. of water containing 120 grams of potassium iodide. After about one-tenth of the iodine solution had been added, the sulfenamide began to separate in the form of white crystals. The reaction mixture was extracted with 700 ml. of ethyl ether, the ether solution washed with water until free from alkali and the ether removed in vacuo. The residue was diluted with water and the solid removed by filtration and dried at room temperature. 45 grams representing a yield of 65.5% of theoretical was obtained as a cream solid, M. P. 55 57 C. Analysis gave 9.89% nitrogen and 22.62% sulfur as compared to 9.78% nitrogen and 22.39%. sulfur calculated for C12H15N202S2.

EXAMPLE 6 5-cafbobutoxy-N-cyclohexyl-4-methyZ 2-thiazolesulfenamide ether and the ether extracts washed until neutral and dried over sodium sulfate.

The'ether was then removed in vacuo, leaving the desired product as the residue. The crude reaction; productwas a dark oil obtained in a yield of grams or 63.9%.

EXAMPLE 7 fi -carbomethoxy-N-isopropyl-4-metiiyl 2 thiazolesalfenamide An aqueous solution containing 45.4 grams (0.24 mole) of 5-carbometlioxy-4-rnethyl-2-thiazolethiol, 77 grams of- 25% aqueous sodium hydroxide in 200 ml. of water, and 141.8 grams (2.4 moles) of monoisopropylamine was prepared in a two liter beaker equipped with a mechanical mixer, dropping funnel, and a thermometer. To this solution at 25 C., there was added, drop by drop, with stirring over a. periodof two hciurs, 91.7- grams of iodine dissolved in 1200 ml. of Water containing grams of potassinm iodide. After about one-tenth of the iodine solution had been added, the sulfenamide began to separate in the form of crystals. The reaction mixture was cooled to 10 C. and the solid then removed by filtration, washed with water until free from alkali and air dried at room temperature. 29' grams representing a yield of 49.1% of a yellow solid, M. P. 57-58 C'., was obtained. Analysis gave 11.50% nitrogen and 25.78% sulfur as compared to. 11.37% nitrogen and 26.03% sulfur calculated for C9H14N2O2S2. V

Employing the procedure of Example 7 but replacing monoisopropylamine with an equirnolecular proportion of n-propylamine 5-carbornethoxy-N-n-propyl-4-rnetl1yl- 2-thiazolesulfenamide is obtained.

EXAMPLE 8 5-carbethoxy-N-isopropyl-4-methyl- Z-thiazbl'esulfenamide An aqueous solution containing 48.8 grams (0.24- moles) of 5-carbethoxy-4-methyl-2-thiazolethiol, 77 grams was prepared in a two liter beaker equipped with a mechanical mixer, dropping funnel and a thermometer. To this solution at 25 C. there was added, drop by drop, with stirring over a period of two hours, 91.7 gramsof iodine in 1200 m1. of water containing 120 grams of potassium iodide. The reaction mixture wasextracted witl 1 700 ml. of ether and the ether solution washed with water until free from alkali and the ether removed in vacuo. The residue was a dark amber oil obtained in a yield of 48% theoretical. Analysis gave 24.10% sulfur as for C1oH 1sN2O2S2.

compared to 24.63% sulfur calculated EXAMPLE9 -carbomethoxy-N tert bmfyl-et-mezhyl: Z-thiazolesulfenamide of 25% aqueous sodium hydroxide .in.:200, ml..of.water. and 141.8 grams (2.4 moles) of ,monoi'sopropylamine.

An aqueous solution containing 48.3' grams (0.25 mole) of S-carbomethoxy-4-methyl-2-thiazolethiol, 80 grams (0.5 mole) of 25% was prepared in a suitable reaction vessel equipped with a mechanical mixer, dropping funnel, and a thermometer.

To this solution was added drop by drop Withagitation over a period of about two hours 64 grams of iodine disaqueous sodium hydroxide in 1000 ml; of water, and 182 grams (2.5 moles) of tert-butylamine ""gen and 23.70%"sulfur calculated for C1oH1sN2O3Sz.

solved in 850 ml. of water containing 69 grams of potassium iodide. The reaction mix was then stirred for an additional minutes and then cooled to about 10 C. The reaction mix was then filtered and the filter cake washed with water until free from alkali, and then dried at room temperature.

nitrogen calculated for C10H16N2O2S2. a h Employing the procedure of Example 9 but replacing tert-butylamine with an equimolecular proportion of isobutylamine 5-carbomethoxy-N-isobutyl-4-methyl-2-thiazolesulfenamide is obtained.

EXAMPLE 10 S-carbethoxy-N-terr-butyl-4-methyl- Z-thiazolesulfenamide An aqueous solution containing 48.8 grams (0.24 mole) of 5-carbethoxy-4-methyl-2-thiazolethiol, 77 grams (0.48 mole) of 25 aqueous sodium hydroxide in 200 ml. of

16 grams of the product was ob tained as a cream colored solid melting at 144 C3 Analysis gave 10.46% nitrogen as compared to 10.75%

water, and 175.2 grams (2.4 moles) of tert-butylamine" was prepared in a suitable reaction vessel equipped with v a mechanical mixer, dropping funnel, and a thermometer.

EXAMPLE ll 5-carb0butoxy-N-zert-butyl-4-methyl- 2-thz'az0lesulfenamide An aqueous solution containing 55.5 grams 0.24 mole) of 5-carbobutoxy-4-methyl-2-thiazolethiol, 80 grams (0.5 mole) of 25% aqueous sodium hydroxide in 200 ml. of water, and 175.2 grams (0.24 mole) of tert-butylamine was prepared in a suitable reaction vessel equipped with a mechanical mixer, dropping funnel, and a thermometer. To this solution was added drop by drop with agitation over a period of about one hour 91.7 grams of iodine dissolved in 1200 ml. of water containing 120 grams of potassium iodide. The reaction was cooled to about 10 C. and then extracted with 500 ml. of diethyl ether. The ether solution was then washed free of alkali with The reaction mix was then filtered' 6 water and the so treated solution dried and! then the ether was removed in vacuo. The product, a tancolore'd "solid; melting at 45-47 C., was, obtained in 70.1% yield; Analysis gave 21.34% sulfur calculated for C13H22N2O2S2.

EXAMPLE 12 sulfur as compared to 21.20%

ml. of water, grams (0.25 mole) of 25% aqueous sodium hydroxide and 222.9 grams (2.5 moles) of 2 p amino-2-methyl1-propanol was'added' drop by drop over* a period ofone hour 91.7 grams of iodine dissolved in 1200 mlbof water containing 120 grams of potassium iodide. The mix was stirred for an additional 30 ininiites: -C. and extracted with5 00 ml. of. diethyl cooled toi 10 ether. The ether extract was washed with water to re *move the alkali, dried, and thenthe ether was removed vacuo. tained in a 29% yield. tane, itinelted at '116118 C. Analysis gave 9.72%- nitrogen and-23.00% sulfur as compared to 10.13% nitro- EXAMPLE 13 'Z-thiazolesulfenaritide To an agitated solution containing 50.9 grams (0.25

The product melting at 108 110" C. was ob- "Upon 'recrystallizing from hep-1::

To an agitated solution'containing 47.3 grams (0.25 mole) of 5 carbomethoxy-4-rnethyl-2-thiazolethiol, 200

mole) of 5-carbethoxy-4-methyl-Z-thiazolethiol, 200 ml. 7

of water, .80 grams (0.25 mole) of 25 aqueous sodium hydroxide and 222.9 grams (2.5 moles) of2-amino-2- methyl-l-propanol was added drop by drop over a period of one and one-half hours 91.7 grams of iodinedissolved in 1200 ml. of water containing grams of potassium was stirred for an additional 6 iodide. The reaction mix two hours and then filtered. The filter cake was then washed free of alkali and dried at room temperature. The product'melting at 9798 34.4% yield. Analysis gave 9.41

calculated for C11H1sN2OsS2.

EXAMPLE 14 To an agitated solution containing 48 grams (0.208-

C. was obtained in a. nitrogen and'22.10% sulfur as compared to 9.64% nitrogen and 22.08% sulfur t mole) of 5-carbobutoxy-4-methyl-2-thiazolethiol, 200 ml. of water, 66.5 grams of 25 aqueous sodium hydroxide and 185.6 grams (2.08 moles) of 2-amino-2-methyl-l-propanol was added, drop by drop over a period of one and one half hours 76.5 grams of iodine dissolved in 1000 ml. of water containing 100 grams of potassium iodide. reaction mix was stirredhalf hours, cooled to 10 C. and filtered. The was then washed free of alkali and dried at room tempera-f ture. The product melting at 68-70 C. was obtained in a 56% yield. Analysis gave 2 0.36% pared to 20.14% sulfur calculated for C13H2zN2O3S2.

The new thiazolesulfenamides are characterized by. strong catalytic activity for accelerating the vulcanization The f for an additional one and onefilter cake i sulfur as com- I of sulfur-vulcanizable rubbers both natural and synthetic. In general the new thiazolesulfenamides provide a degree of processing safety unattainable with accelerators heretofore available. to the new thiazolesulfenamides wherein R" of the afore described structural formula is a 6-membered hetero! This is particularly true with respect I cyclic secondary amine residue containing not more than two hetero atoms, one of which being nitrogen, and at.

and consisting of carto the hetero atom (or I least four carbon atoms in the ring bon and hydrogen atoms in addition i i'.

'The. powerful accelerating properties as well as the marked delayed action of the group of new thiazolesulfenamides wherein R is a 6-membe red heterocyclicsec ondary amine residue is illustrated by comparison to'the commercial delayed action accelerator N-cyclohexyl 2- benzothiazolesulfenamide in a stock containing furnace carbon black. The inclusion of furnace type carbon black is significant because these blacks do not possess the retarding properties inherent with channel black so that stocks compounded with furnace black tend to cure during processing.

The stocks so compounded were cured in the usual manner by heating in apress for 30'minutes at 144 C. The physical properties of the vulcanizates illustrate the powerful accelerating action of the new compounds.

TABLE I Modulus of Elasticity Tensile at Ultimate Stock in lbs. lin. Break in Elongation,

at Elongalbs/in. percent tlonof 300% In addition the processing safety of the vulcanizable compositions was evaluated'by' means'of a Mooney plastometer at 121 C. The time to prevulcanize or scorch is taken as the time in minutes at which the plasticity curve begins to rise continuously and sharply.

TABLE II' Mooney Scorch Stock in mins. at

Several 5-carbalkoxy N,N-dialkyl-2-thiazolesulfenamides have also been prepared and characterized but not one of themprovided an element of processing safety comparable; to the thiazolesulfenamides of this invention wherein R" of the' aforedescribed structural formula is a he'terocyclic secondary amine residue. In similar rubber formulations 5 carbethoxy N,N' die'thyl'-'4 methyl- Z-thiazol'esulfenamide, anamber oil; andS-Ca'rboniethdxy- N,N-diethyl-4-methyl-2-thiazolesulfenamide, a yellow solid, M: P. 39 C. (nitrogen 11.00%, sulfur 24.49% as compared to nitrogen 10.76% and sulfur 24.63% calculated'for CiH'16N202S2)' were greatly inferior to 4 (5- ca rbethoxy-4=rnethyl-Z-thiazolylsulfenyl)niorpholine. The Mooneyscorch' times at 121 C. were in'each instance for the 5'-carbalkoxy-N,N-dialkyl-2rthiazolesulfenarnides only about one-half thatof'the commercial delayed action acceler'ator N-cyclohexyl-2 benzothiazolesulfenamide. Additionally H 5=carbomethoxy-N,N=di-isopropyl 4-methyl-2- thia'zolesulfenamide, anamber. oil (nitrogen 9.47% and sulfur" 22.84% as compared to 9.71% nitrogen and 22.23% sulfurcalculated forCm'HQoN'zSaO'z) was prepared and evaluated in a rubber formulation and found to ex 8 hibit less delayedaction thanthat' employing N-cyclohexyl-Z-benzothiazolesulfenamide as the vulcanization accelerator.

As an example ofdelayed action in a' gum stock, againas compared to the same commercial delayed action accelerator, rubber stocks were compounded comprising:

Stock o D Parts by weight Sulfur N-Oyclohexyl 2-benzothiazolesulfenamide 1 4-Methyl-2(kmorpholinylsulfenyl)5-thiazolecarboxylic acid The Stocks so compounded were cured in the usual manner by heating in a press for 30 and 60 minutes at C. It will be noted from the cure results that the delayed action of the carboxyl substituted sulfenamide was so great that no cure at allwas obtained in 30 minutes although the 60 minute cure shows accelerating strength comparable to the commercial control.

TABLE III Modulus of Elasticity in lbs/1'11. Mms. at Elongation of 500% .Tensile at Break in lbs/in.

Ultimate Elongation, percent Stock 1, 540 4, no cure In addition the processing safety was evaluated using.

the Mooney plastometer in the manner described. The stock containing the carboxyl substituted sulfenamide showed no evidence of scorch for the duration of the test.

TABLE IV Mooney scorch Stock inminsat As still further examples of accelerating activity and processing safety in the presence of furnace carbon black, rubber stocks were compounded comprisin Stock E G Parts by weight Pale crepe rubber Furnace carbon black Zinc oxide Saturated hydrocarbon softener. Stearic acid Sulfur Condensation product of p-amino biphenyl and acetone am e 4-(5-Carbomethoxy-4-methyl-2-thiazolylsulfenybmorpholine 4-(5-Carbethoxy-4-methyl-2-thiazolylsulienyhmorpholine 4-Methyl 2 4-rnorpho1inylsulfenyl) 5-thiazolecarboxylic acid The stocks so compounded were cured in the usual manner by heating in a press for 30 minutes at 144 C. The accelerating activity was comparable to that of the vcommercial'control in every case. The data are set forth below:

asnaaaas M TABLEV The-.stockszso=:compound .werefcurediby heating Iirtia Press at 144% 1 a 1 Modulusot' z V Elasticity Tensile at Ultimate ,TABLE m Stock in lbs/in. Break in Elongation, 7 A atElongalbs/in. percent 5' d i 5 I non of 9 Elasticity Tensile at Ultimate inIbs/imiv ,Breakigi Elongation, g----- g ggg 'ggg gggi tilt? ,r f G; 31 056 4121a g j Q 436 300% H- 2, 850 4, 125 430 I, H quired forprevulcanization was evalu- ,60 1:843 a, 3Z27o- 535 ated by th Mq,0'ney plastometer ingthe manner'above- Q38 g8 described. It' will'b'e noted that all'of the accler ors 1:960 90 "1935 3,325- 490v are of the delayed action type. 90 21070 3,100 445 TABLE VI 0:: q a Mooney Scorch The processing safety-was evaluatedp at 135 CJem-T Stock inmiglfj at a ertin h 992 9! pl stomete a 'd e T A VVVVV Navies." it r g r r ,TAB EV i *1 1% V Mooney Scorch c+ A Stock. 7 v inminsat' H i Q 1 Similar tests were carried out with formulations 38 comprising? i 28 .7 t, n. 1: I 26- Stock 1-; Q '1" KS;

' v 30 The new sulfenamides show marked acceleration in y weight butyl rubber although theorder of activity is not necessarily the same as in naturalrrubber. The following comcrepe g g 2g i g positions were cured by heating in a press for different Z311: d i l age '1 2. periods of time at 165.5 C.- p-Quinone dioxime is a well- Ste'aric acid; 2 2" "'2 a i 1 Samated by eat one ener" A 3 v .3 7 s3 known accelerator and vulc mz ng agent especial y Sulfur-"1--.; 2,5 recommended for this polymer. N-Cyclohexyl 2-benzothiazoles1flienam1de 0.8 l i i 7 fi-Carbomethoxy-N -eyclohexyl-4-metl1 yl-2- i t V V thiazolesulfenamide 0. 8 r i v. t t t 5-Oarbomethoxy-N-isopropyl-4-methyl-2- 7 Stock Q R s thiazolesuli'e 0.8

i 40 H Parts by weight The stocks so compounded were cured by heating in a press for 30 minutes at 144 C. Additionally the v 100 100 Q 50 50 scorch time was determmed at 121 C. employmg the 5 5 M 11 "'la' om te a e ibe 1 1 oo ey p st e r s d scr d Sum L5 1.5

i: T E V11 -'Lead dioxide"... 10 10 a c .c ggunoge die imeth 1 1 v v ar 01118 OXY' -me y 1820 y Modulp-sof T H U1 Mooney su1fenyl( morpholine 6 3185mm ens SW91 s-oarbothoxy-Nuso ro i-t-moth l-z- 2 1 3 6 fhimnln nlfpnnmiria 1 tionrofmfim p Mercaptobenzothiazole (t5 2,893 3,906 i 406 9 TABLE X 2, 740 3,000 400 s r 2,930 3,466 V 7366 H 10 M dulusof t v to S TQure1n liliagtieity 'lgensillteialt EllJltimgte Replacing ::the11accelerator by 5-carbomethoxy-N,N-di- 55. E i g; t figj z 855 1 2 ethyl-4-methy1-2-thiazolesulfenamide in the foregoing @33 9 formulation resulted in acompound having inadequate A processing safety. V j V M 1 p 6 1323 2137 As illustrative of the properties in a synthetic rubber o "555 1: 20 26 stock compositions werecompounded comprising; w 88 7 9 538 Y I I r j r 90 "82s 1:686 .770 stock "V V V M "N O P 90 11480 11660 610 Parts by weight It is of interest that replacement of 4-(5-carbomethoxy-- 4-methyl-2-thiazolylsulfenyl)morpholine I by the same GR-S-l00 100 .100 100 100 Furnacearbon black 50 50 50 50 amount o 4 carbethoxv 4 yl 2 z y Saturated hydrocarbon softener 10 10 10 1o sulfenyl)morphol1ne resulted 1n weak accelerating action, Zinc 9 4 4 4 4 the modulus and tensilestrength of the vulcanizates being Steal-1c acid" V. 2 2 2 2 Sulfur 1.75 1. 75 1.75 1. 75 no more than half those shown above although the comi iii i i f 1 2 g pounds are comparable in other type polymers. The 4- s oari%iiioiigfi g gh i-z-thie oiyl- 1 2 stock containing p-quinone dioxime cured during the pre- 8 any morp G e 4 (543Mbmethoxy4 methy1 2 thia heatlngpenod before any readings could be recorded on Z 0l gsulre t r i) moiphtislinefi I 4 1.2 the Mooney plastometer. Stock R showed no evidence 81 01116 oxyopropy n methymthmolesunemmide M of cure after. 30 m nutes at 1305 C. and the scorch time ofStockSwasSmmutes. 7:.- t v r 11 "Further examples of the new sulfenamideswere 'eval uated in natural rubber compositions and were found to exhibit marked delayed action. However, at curing temperature they exhibited fast accelerating action. Compositions were compounded comprising:

Stock T U Parts by weight Smoked sheets rubber... Furnace carbon black Zinc oxide rbon softener.

The stocks so compounded were cured in the usual manner by heating in a press for different periods of time at 142 C. The physical properties exhibitedby the minute cures are reproduced below and indicate that the compounds are fast powerful accelerators at curing temperature.

TABLE XI Modulus of Elasticity Tensile at Ultimate Stock lbs/in. Break in Elongation at Elonga- 1bs.li.u. percent tion of In spite of the activity at curing temperature, the compositions were relatively inactive at lower temperatures.

Thus, the processing safety was evaluated by means of the Mooney plastometer as described. 7

TABLE XII Stock aim" 0. at iss o.

Additionally as illustrative of the vulcanization accelerating properties of the new thiazolesulfenamides of this Mooney Scorch in Mins.

Dirk,

invention rubber compositions were compounded comprising:

Stock W X 7 Parts by weight Smoked sheets rubber 100 100 Furnace carbon black 50 50 Zinc oxide 6 5 Stearic acid 2 2 Saturated hydrocarbon softener. 3 3 S ur 2. 5 2. 5 N-Gyelohexyl-2rbenzothiazolesulfen O. 8 N-tert-Buty S-carbethoxy-4-methyl-2-thia fenamide 4;- 0. 8

The stocks so compounded were cured in the usual manner by heating in a press for 15 minutesat 142. C. The physical properties obtained are set forth below:

TABLE XIII Modulus of Elasticity Tensile at Ult. Mooney Stock in lbs/in. Break in Elong., Scorch in at ElongalbsJin. Percent mins. at

tion of 121 0.

As still further illustrative of the vulcanization accelerating properties of the thiazolesulfenamides of this invention synthetic rubber stocks were compounded coinprising: V a

The stocks so compounded were cured in the usual manner by heating in ,a press for minutes at 144 C. The physical properties obtained are set forth below as well as the scorch times of the respective stocks as measured by the Mooney plastometer at 135 C.

TABLE XIV Modulus of Elasticity Tensile at Ult. Mooney Stock in lbs/in. Break in Elong., Scorch in at Elongalbs/in. Percent wins. at

tion of 135 C.

As further illustrative of the vulcanization accelerating properties of the thiazolesulfenamides of this invention 7 natural rubber stocks were compounded comprising:

Stock--- En FF Parts by weight Smoked sheets rubber .L 100 Furnace carbon black 50 50 Zinc oxide 5 6 Stearic acid 2 2 Saturated hydrocarbon softener 3 3 ulfur r 2. 5 2. 5 N-Cyclohexyl 2-benzothiazolesulfenamide 0. 8 5-Oarb0meth0xy-N (hydmxy-tert-hutyD-4-methyl- 2-thiazolesulfenamide 0. 8

The stocks so compounded were cured in the usual manner by heating in a press for 15 minutes at 142 C. The

physical properties obtained are set forth below:

TABLE XV Modulus of Elasticity Tensile at Ultimate Stock in lbs/in. Break in Elongation,

at ElongalbsJin. percent tion of 300% E1; 2,790 3,595. 435' FF 2, 585 3, 835 450 13 p The scorch times of stocks EE and FF as measured on the Mooney plastometer at 121 C. were found to be the same, namely 16 minutes.

The new sulfenamides form reaction products with dimethylolurea which are valuable accelerators. Similarly they form addition products with zinc chlorid The zinc chloride adducts possess accelerating activity comparable to the parent materials. Zinc chloride adducts are formed by associating a solution of zinc chloride with a solution of the sulfenamide. For example, admixing anhydrous ether solutions of 4-(5-carbomethoxy-4-methyl-2-thiazolylsulfenyl)morpholine and zinc chloride U. S. P. resulted in precipitation of the desired addition product. After standing 20 hours the solids were filtered off. The product melted at 95100 C. Analysis indicated that a mole to mole addition product formed. The solid product obtained in similar manner from zinc chloride and 4 (5 carbethoxy-4-methyl-2-thiazolylsulfenyl) morpholine melted at 7585 C. Again analysis indicated that a mole to mole addition product was formed.

By the term sulfur-vulcanizable rubber as employed in the specification and claims is meant to include natural as well as synthetic rubbers which are capable of vulcanization when heated with sulfur and is intended to include latices and reclaims thereof whether or not admixed with fillers, softeners, pigments, antioxidants, etc.

While this invention has been described with respect to certain embodiments it is not so limited and it is to be understood that various changes and modifications may be made without departing from the spirit or scope of this invention.

This case is a continuation-in-part of application Serial No. 294,929, filed June 21, 1952 now abandoned. A continuation-in-part of application Serial No. 294,929 matured as U. S. Patent 2,766,237.

What is claimed is:

1. The method of vulcanizing a sulfur-vulcanizable rubber which comprises heating a sulfur-vulcanizable rubber, sulfur and a thiazolesulfenamide of the structural formula where n is a whole number less than 3, where R and R are selected from the group consisting of hydrogen and hydrocarbon radicals, and where R" is selected from the group consisting of primary amine residues and 6- membered heterocyclic secondary amine residues containing a hetero nitrogen atom attached to the sulfur atom.

2. The method of vulcanizing a sulfur-vulcanizable rubber which comprises heating a sulfur-vulcanizable rubber, sulfur and a thiazolesulfenamide of the structural formula where n is a whole number less than 3, where R and R are short chain alkyl radicals, and where R is a 6- membered heterocyclic secondary amine residue containing not more than two hetero atoms, one of which being a nitrogen atom which is attached to the sulfur atom, and containing at least four carbon atoms in the ring and consisting of carbon and hydrogen atoms in addition to the hetero atoms.

3. The method of vulcanizing a sulfur-vulcanizable rubber which comprises heating a sulfur-vulcanizable 1'4 rubber, sulfur and a thiazolesulfenamide of the structural formula where R, R and A are short chain alkyl radicals.

4. The method of vulcanizing a sulfur-vulcanizable rubber which comprises heating a .sulfur-vulcanizable rubber, sulfur, furnace carbon black, and a thiazolesulfenamide of the structural formula CHa- C-N where R" is a 6-membered heterocyclic secondary amine residue containing not more than two hetero atoms, one of which being a nitrogen atom which is attached to the sulfur atom, and containing at least four carbon atoms in the ring and consisting of carbon and hydrogen atoms in addition to the hetero atoms.

5. The method of vulcanizing a sulfur-vulcanizable rubber which comprises heating a sulfur-vulcanizablc rubber, sulfur, furnace carbon black, and a thiazolesulfenamide of the structural formula 9. The method of vulcanizing a sulfur-vulcaniza'ble' rubber which comprises heating natural rubber, sulfur and 5 carbomethoxy N isopropyl 4 methyl-2- thiazolesulfenamide.

10. The method of vulcanizing a sulfur-vulcanizable rubber which comprises heating natural rubber, sulfur and 5 carbethoxy N tert butyl-4-methyl-2-thiazolesulfenamide.

11. The of claim 1.

12. The of vulcanizate obtained by the process vulcanizate obtained by the process claim 6.

13. The claim 7.

14. The claim 8.

15. The claim 9.

16. The

claim 10.

vulcanizate obtained by the process vulcanizate obtained by the by the process vulcanizate obtained process of vulcanizate obtained by the process of References Cited in the file of this patent UNITED STATES PATENTS 2,342,545 Jones Feb. 22, 1944 

1. THE METHOD OF VULCANIZING A SULFUR-VULCANIZABLE RUBBER WHICH COMPRISES HEATING A SULFUR-VULCANIZABLE RUBBER, SULFUR AND A THIAZOLESULFENAMIDE OF THE STRUCTURAL FORMULA 